Multilayer ceramic electronic device

ABSTRACT

A multilayer ceramic electronic device comprising: a ceramic element body, in which a plurality of dielectric layers and a plurality of internal electrode layers are alternately stacked, and at least a pair of external electrodes which are connected to the internal electrode layers on surfaces of the ceramic element body; a thickness of the dielectric layers is 0.4 μm or less, a width (W 0 ) of the ceramic element body along a width-direction is 0.59 mm or less, a gap (Wgap) between an outer face of the ceramic element body and an end of the internal electrode layers along width-direction of the ceramic element body is 0.010 to 0.025 mm, and a ratio (Wgap/W 0 ) of the gap with respect to the width is 0.025 or more.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a multilayer ceramic electronic devicein which dielectric layers are extremely thin.

2. Description of the Related Art

Together with miniaturization and thinning of electronic equipment,miniaturization and thinning of the multilayer ceramic electronic devicestored therein are requested. Thus, thinning of the dielectric layers inthe multilayer ceramic electronic device is requested.

As described in Patent Article 1, it is known to generate cracks duringmanufacturing in case that the dielectric layers in the multilayerceramic electronic device are made thin, and a method to prevent thecracks is being developed.

However, although the conventional limit of the thickness of thedielectric layer was 1 μm or so, a technology making the thickness ofthe dielectric layer 0.5 μm or less is being developed with the recenttechnological innovation. Conventionally, a technology, consideringmeans to prevent generation of the cracks and to ensure a capacitance incase that the thickness of the dielectric layer is made 0.5 μm or less,further 0.4 μm or less, has not been established.

[Patent Article 1] Japanese Unexamined Patent Publication No. H7-74047

SUMMARY OF THE INVENTION

The present invention has been made by considering the abovecircumstances, and a purpose of the present invention is to provide themultilayer ceramic electronic device which is capable of preventinggeneration of the cracks and of preventing drop of the capacitance, evenwhen the thickness of the dielectric layers is made thin.

As a result of intensive studies of the above purpose, the presentinventors has attained providing the multilayer ceramic electronicdevice which is capable of preventing generation of the cracks and ofpreventing drop of the capacitance, even when the thickness of thedielectric layers is 0.5 μm or less, further 0.4 μm or less, only bysatisfying the specific dimensional relation, which lead to a completionof the invention.

Namely, the multilayer ceramic electronic device of the inventionincludes a ceramic element body, in which a plurality of dielectriclayers and a plurality of internal electrode layers are alternatelystacked, and at least a pair of external electrodes which are connectedto the internal electrode layers on the surface of the ceramic elementbody, wherein the thickness of the dielectric layers is 0.4 μm or less,a width (W0) of the ceramic element body along width-direction is 0.59mm or less, a gap (Wgap) between an outer face of the ceramic elementbody and an end of the internal electrode layers along width-directionof the ceramic element body is 0.010 to 0.025 mm, and a ratio (Wgap/W0)of the gap with respect to the width is 0.025 or more.

According to the invention, the multilayer ceramic electronic devicewhich is capable of preventing generation of the cracks and ofpreventing drop of the capacitance, even when the thickness of thedielectric layers is 0.5 μm or less, and further 0.4 μm or less.

A ratio (te/td) of the thickness (te) of the internal electrode layerswith respect to the thickness (td) of the dielectric layers ispreferably 1.05 or less.

In case that an average grain size of the first dielectric grainsconstituting the dielectric layer placed between the internal electrodelayers along the laminating direction is Di and an average grain size ofthe second dielectric grains in an exterior area placed outside of thelaminating direction of an interior area in which the internal electrodelayers are laminated interposing the dielectric layers along thelaminating direction is Dg, Dg/Di≧1 is preferably satisfied.

In case that the average grain size of the first dielectric grainsconstituting the dielectric layers placed between the internal electrodelayers along the laminating direction is Di, and an average grain sizeof the third dielectric grains constituting a lead-out area placedbetween the lead-out parts of the internal electrode layers connected toeither one of the external electrode is Dh, Dh/Di≧1 is preferablysatisfied.

With the relations above, the capacitance further improves even thedielectric layers are thinned. It has been generally reported that thespecific permittivity decreases as the dielectric layers become thin.However, the present inventors have found that decrease of the specificpermittivity can be prevented even the dielectric layers become thin bycontrolling the grain size of the dielectric grains in specific areas.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view of the multilayer ceramiccapacitor according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of FIG. 1 along line II-II.

FIG. 3 is a schematic cross-sectional view showing the laminatingprocess of green sheet in manufacturing process of the multilayerceramic capacitor as shown in FIG. 1.

FIG. 4 is a plane view showing a part of a pattern of the internalelectrode layer of FIG. 3 along line IV-IV.

FIG. 5A is a schematic cross-sectional view parallel to X-Z axis planeof a laminated body after laminating the green sheet shown in FIG. 3.

FIG. 5B is an enlarged schematic cross-sectional view parallel to Y-Zaxis plane of a laminated body after laminating the green sheet shown inFIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, the present invention will be described based on theembodiments shown by the figures.

Overall Structure of the Multilayer Ceramic Capacitor

First, an overall structure of the multilayer ceramic capacitor as anembodiment of the multilayer ceramic element component according to thepresent invention will be described.

As is shown in FIG. 1, multilayer ceramic capacitor 2 according to thepresent embodiment has a capacitor element body 4, the first terminalelectrode 6 and the second terminal electrode 8. The capacitor elementbody 4 has inside dielectric layers 10 and internal electrode layers 12,in which the internal electrode layers 12 are alternately stackedbetween the inside dielectric layers 10. A part where the insidedielectric layers 10 and the internal electrode layers 12 arealternately stacked is an interior area 13.

The capacitor element body 4 has the exterior area 11 on both ends ofthe laminating direction Z (Z-axis) thereof. The exterior area 11 isformed by laminating a plurality of the dielectric layers, which arethicker than the inside dielectric layers 10 constituting the interiorarea 13.

One alternately stacked internal electrode layers 12 has a lead-out part12A electrically connected to inside of the first terminal electrode 6,which is formed outside of the first end of the capacitor element body 4in Y-axis direction. Further, the other alternately stacked internalelectrode layers 12 has a lead-out part 12B electrically connected toinside of the second terminal electrode 8, which is formed outside ofthe second end of the capacitor element body 4 in Y-axis direction.

The interior area 13 has the capacitance region 14 and the lead-outareas 15A, 15B. The capacitance region 14 is a region where the internalelectrode layers 12 are stacked sandwiching the inside dielectric layers10 along the laminating direction. The lead-out area 15A is an areabetween the lead-out parts 12A of the internal electrode layers 12connected to the external electrode 6. The lead-out area 15B is an areabetween the lead-out parts 12B of the internal electrode layers 12connected to the external electrode 8.

As shown in FIG. 2, the side protection region 16 is formed on both endsof the capacitor element body 4 in X-axis direction. The side protectionregion 16 is configured by the same or the different dielectric materialconfiguring the dielectric layers of inside dielectric layers 10 and/orthe exterior area 11. Further, the lead-out areas 15A and 15B areconfigured by the same or the different dielectric material configuringthe dielectric layers of inside dielectric layers 10.

Materials of the dielectric layers configuring the inside dielectriclayers 10 and the exterior area 11 may be the same or different; theyare not particularly limited and may be the dielectric materials havingthe perovskite structure such as ABO₃. In said ABO₃, “A” is at least akind of Ca, Ba, Sr and so on and “B” is at least a kind of Ti, Zr and soon. Mole ratio of A/B is not particularly limited and is 0.980 to 1.020.

Although materials of the internal electrode layers 12 are notparticularly limited, metals of Ni, Cu, Ag, Pd, Al and so on, and theiralloys can be used.

Although materials of the terminal electrodes 6 and 8 are notparticularly limited, at least a kind of Ni, Pd, Ag, Au, Cu, Pt, Rh, Ru,Ir and so on, or their alloys may be used. Generally, Cu, Cu alloys, Ni,Ni alloys, Ag, Ag—Pd alloys, In—Ga alloys and so on may be used.

Size and formation of the multilayer ceramic capacitor 2 can be suitablydetermined according to the application or the purpose thereof. In casethat the multilayer ceramic capacitor 2 has a rectangular parallelepipedshape, the lengthwise L0 (see FIG. 1) is generally 0.2 to 5.7 mm,however, it is preferably 0.3 to 3.2 mm, more preferably 0.38 to 2.1 mmand the most preferably 0.38 to 1.60 mm in the present embodiment.

Note in FIG. 1, although a length of the capacitor element body 4 inY-axis direction is drawn as the lengthwise L0 of the multilayer ceramiccapacitor 2, it is almost the same with the length of the multilayerceramic capacitor 2 in Y-axis direction including the terminalelectrodes 6 and 8. Although the thickness of the terminal electrodes 6and 8 is drawn thicker than the actual to easily show by the figures, itis 10 to 50 μm or so each in practice, and is extremely thin relative tothe lengthwise L0. Further, in the figures, X-axis, Y-axis and Z-axisare mutually perpendicular, Z-axis corresponds to the laminationdirection of the inside dielectric layers 10 and the internal electrodelayers 12, and Y-axis corresponds to a direction in which the lead-outareas 15A and 15B (the lead-out parts 12A and 12B) are formed.

As shown in FIG. 2, a height H0 of the multilayer ceramic capacitor 2varies according to laminating numbers of the inside dielectric layer 10and the internal electrode layers 12. H0 is generally 0.2 to 3.2 mm andpreferably 0.2 to 1.6 mm in the present embodiment. Although the heightH0 of the multilayer ceramic capacitor 2 is drawn as the thickness ofthe capacitor element body 4 in Z-axis direction in FIG. 2, H0 is almostthe same with the thickness including the terminal electrodes 6 and 8 inFIG. 1, since thickness of the terminal electrodes 6 and 8 issufficiently thin.

Although the width W0 of the multilayer ceramic capacitor 2 is generally0.2 to 5.0 mm, it is 0.59 mm or less, preferably 0.10 to 0.59 mm, morepreferably 0.15 to 0.59 mm, and the most preferably 0.185 to 0.47 mm inthe present embodiment. In case that the thickness of the dielectriclayers is 0.4 μm or less, cracks are easy to generate to the capacitorelement body after manufacturing when the width W0 becomes excessivelylarge. The following can be considered for such cause.

In case that the thickness of the dielectric layers becomes thin, it isconceivable that density of the internal electrode layers in an interiorarea 13, which is a capacitance formation section, becomes relativelylarge, and stresses operating between the internal electrodes and theceramic layers configuring the side protection region 16 or the exteriorarea 11 during firing becomes large. In particular, in case that thethickness of the dielectric layers is 0.4 μm or less and the width W0 is0.80 mm or more, the density of the internal electrode at the interiorarea 13 which is the capacitance formation section becomes large andfurther, an area (a volume) occupying in the ceramic capacitor becomeslarge; and that effect of the stress becomes large and the cracks areeasily generated.

Although the thickness td (see FIG. 2) of each inside dielectric layers10 is generally several micrometers to several ten micrometers, it is0.4 μm or less, preferably 0.4 to 0.1 μm, and the most preferably 0.4 to0.3 μm in the present embodiment. It is preferable that the thickness to(see FIG. 2) of internal electrode layers 12 is almost the same with thethickness of the inside dielectric layers 10, more preferably te/td isdetermined 1.25 or less, and the most preferably te/td is determined0.95 to 1.05. The crack preventing effect is improved with theconstitution above.

In the present embodiment, width Wgap of each side protection region 16in X-axis direction shown in FIG. 2 matches with the gap from the outersurface (an end face in X-axial direction) of ceramic element body 4 tothe end of internal electrode layers 12 along the width direction(X-axial direction) of the ceramic element body 4. This width Wgap is0.010 to 0.025 mm, and preferably 0.015 to 0.025 mm. The cracks tend tooccur in case that the width Wgap is excessively small, while decreaseof the capacitance tends to be significant when the width Wgap isexcessively large.

This width Wgap is determined considering the width W0 of capacitor 2,and in the present embodiment, the ratio Wgap/W0 is 0.025 or more; thecrack tends to generate in case said ratio is excessively small. Noteeach width Wgap of each side protection region 16 in X-axis directionformed on both sides of the capacitor element body 4 in X-axis directionmay be mutually the same or different only when the above conditions arefulfilled.

Although the thickness “t0” (see FIG. 1) of the exterior area 11 is notparticularly limited, it is in a range of preferably 15 to 200 μm, andmore preferably 15 to 80 μm. By setting the thickness t0 within suchrange, the cracks are suppressed, the internal electrode layers 12 andthe inside dielectric layer 10 are protected, and it also contribute tothe reduction in size. Each thickness t0 of the exterior area 11 formedon both ends of the capacitor element body 4 in Z-axis direction may bemutually the same or different only when the above conditions arefulfilled.

In particular, in the present embodiment, in case that an average grainsize of the first dielectric grains constituting the inside dielectriclayer 10 is Di and an average grain size of the second dielectric grainsplaced in the exterior area 11 is Dg, Dg/Di≧1 is preferably satisfied,Dg/Di≧1.05 is more preferably satisfied, and Dg/Di≧1.15 is the mostpreferably satisfied. With the constitution above, the capacitancefurther improves even when the dielectric layers are thinned. It hasbeen reported in general that the specific permittivity tends todecrease along with thinning of the dielectric layers. However, thepresent inventors have found that the decrease of the specificpermittivity can be prevented even when the dielectric layers arethinned by controlling the grain size of the dielectric grains in thespecific areas.

Further, in the present embodiment, in case that an average grain sizeof the first dielectric grains constituting the inside dielectric layer10 is Di and an average grain size of the third dielectric grainsconstituting lead-out areas 15A and 15B is Dh, Dh/Di≧1 is preferablysatisfied, Dh/Di≧1.1 is more preferably satisfied, and Dh/Di≧1.2 is themost preferably satisfied. With the constitution above, the capacitancefurther improves even when the dielectric layers are thinned. It hasbeen reported in general that the specific permittivity tends todecrease along with thinning of the dielectric layers. However, thepresent inventors have found that the decrease of the specificpermittivity can be prevented even when the dielectric layers arethinned by controlling the grain size of the dielectric grains in thespecific areas.

The reason to suppress decrease of the specific permittivity even whenthe dielectric layers are thinned may be considered as following.

Namely, it is conceivable that compressive stress is provided to thedielectric of the capacitance region 14 by making the average grain ofthe dielectric grains in the capacitance region 14 larger than theaverage grain of the dielectric grains constituting the exterior area 11or the lead-out areas 15A and 15B. Thus, the specific permittivity isconceivable to improve. Although the dielectric of the capacitanceregion 14 of the multilayer ceramic capacitor 2 has polycrystal body andthat compression direction thereof is not limited, it is conceivablethat making crystal grain size of the dielectric of the exterior area 11or the lead-out areas 15A and 15B large contributes to an improvement ofthe specific permittivity.

In particular, it was confirmed that it was particularly effective whenthe thickness of the inside dielectric layers 10 is 0.5 μm or less. Incase that the dielectric layers are thicker than 0.5 μm, the specificpermittivity is high without providing the compressive stress (withoutcontrolling the grain ratio) to the dielectric of the capacitance regionin the multilayer ceramic capacitor. While when the dielectric layersare 0.5 μm or less, the decrease of the specific permittivity isprevented, and the specific permittivity can be improved on thecontrary.

From these viewpoints, this can also be said to the dielectric grains inthe side protection region 16, which can be constituted with the samedielectric grains in the lead-out areas 15A and 15B. Namely, in casethat the average grain size of the first dielectric particlesconstituting the inside dielectric layers 10 is Di and the average grainsize of the forth dielectric grains constituting the side protectionregion 16 is Dh′, Dh′/Di≧1 is preferably satisfied, Dh′/Di≧1.1 is morepreferably satisfied, and Dh′/Di≧1.2 is the most preferably satisfied.

Method for Manufacturing the Multilayer Ceramic Capacitor

Next, a method for manufacturing the multilayer ceramic capacitor 2 asan embodiment of the invention will be described.

First, a paste for an inside green sheet and a paste for an outsidegreen sheet are prepared in order to manufacture an inside green sheet10 a constituting the inside dielectric layer 10 and an outside greensheet 11 a constituting an outside dielectric layer of an exterior area11, after firing shown in FIG. 1.

The paste for the inside green sheet and the paste for the outside greensheet are generally composed of an organic solvent based paste, obtainedby kneading ceramic powders and an organic vehicle, or a water basedpaste.

Materials of the ceramic powders are suitably selected from variouscompounds which become composite oxides or oxides, such as carbonates,nitrates, hydro oxides, the organic metal compounds and so on; and usedby mixing thereof. Materials of the ceramic powders are used as powdershaving the average particle size of 0.45 μm or less, and preferably 0.1to 0.3 μm or so in the present embodiment. Note it is desirable to usethe powders finer than the thickness of the green sheet in order to makethe inside green sheet extremely thin.

The organic vehicle is obtained by dissolving a binder in the organicsolvent. The binder used for the organic vehicle is not particularlylimited, and may be suitably selected from various kinds of generalbinders such as ethyl cellulose, polyvinyl butyral, etc.

The organic solvent is also not particularly limited and may be suitablyselected from various kinds of the organic solvents, such as terpineol,butyl carbitol, acetone, toluene, etc., according to a process of use,such as a printing process or a sheet process.

The paste for the green sheet may include additives selected from avariety of dispersants, plasticizers, dielectrics, subcomponentcompounds, glass frits, insulators and so on, according to needs.

As the plasticizers, phthalic esters, such as dioctyl phthalate orbenzylbutyl phthalate and so on, adipic acids, phosphoric esters,glycols and so on can be exemplified.

Next, a paste for internal electrode pattern layer forming the internalelectrode layers 12 shown in FIG. 1 is prepared. The paste for internalelectrode pattern layers is prepared by kneading the conductivematerials, constituted by the abovementioned various conductive metalsand alloys thereof, or various oxides, organic metal compounds,resinates, etc., which become the above-mentioned conductive materialsafter firing, and the abovementioned organic vehicle. The paste forinternal electrode pattern layers may include ceramic powder as aninhibitor, when required. Note said inhibitor works to prevent sinteringof the conductive powders during the firing process.

By using the paste for the inside green sheet and the paste for internalelectrode pattern layer prepared above, the internal laminated body 13a, which becomes the interior area 13 after firing, is manufactured byalternately laminating the inside green sheet 10 a, which becomes theinside dielectric layer 10 after firing, and the internal electrodepattern layer 12 a, which becomes the internal electrode layers 12 afterfiring, as shown in FIG. 3. Further, after or before manufacturing theinternal laminated body 13 a, the outside green sheet 11 a, whichbecomes an outside dielectric layer of the exterior area 11 after firingis formed by using the paste for the outside green sheet.

In concrete, the inside green sheet 10 a is formed on the carrier sheet(e.g. PET film) as support such as by doctor blade, at first. The insidegreen sheet 10 a is dried after formed on the carrier sheet.

Next, the inside green sheet 10 a having the internal electrode patternlayer 12 a is obtained by forming the internal electrode pattern layer12 a on the inside green sheet 10 a formed as described above by usingthe paste for internal electrode pattern layer. Then, said inside greensheets 10 a having the internal electrode pattern layers 12 a arealternately laminated and the internal laminated body 13 a is obtained.Although formation method of the internal electrode pattern layer 12 ais not particularly limited, printing process, transfer process and soon may be mentioned. Note the inside green sheets 10 a having theinternal electrode pattern layers 12 a can be laminated via the adhesivelayers.

Similar to the inside green sheet 10 a, the outside green sheet 11 a isformed on the carrier sheet as the support. The outside green sheet 11 ais dried after forming on the carrier sheet. Note the thickness of theoutside green sheet 11 a is sufficiently thicker than the inside greensheet 10 a.

As shown in FIG. 4, the internal electrode pattern layers 12 a areformed on surfaces of the inside green sheets 10 a; and therebetween, agap 30 along a longitudinal direction Y of the internal electrodepattern layer 12 a and a gap 32 along a short-length direction X of theinternal electrode pattern layer 12 a are formed, which have the latticepattern in the plan views. Within the gaps 30 and 32 of the latticepattern, step absorbing layers 20 shown in FIG. 3 can be formed. NoteFIG. 3 only shows the gap 32.

Forming the step absorbing layers 20 in these gaps 30 and 32 willeliminate difference in level on the surface of the green sheet 10 a dueto the internal electrode pattern layer 12 a; and this will alsocontributes to deformation prevention of the finally obtained thecapacitor element body 4. The step absorbing layers 20 is formed by suchas printing process, similar with e.g. the internal electrode patternlayer 12 a. The step absorbing layers 20 include the ceramic powders andthe organic vehicle, similar with the green sheet 10 a. The stepabsorbing layers 20, however, unlike the green sheet 11 a, is formed byprinting; and that it is adjusted easy to print. Although the printingprocess is not particularly limited, screen printing, gravure printingand so on is mentioned, and the screen printing is preferable.

An organic binder component (polymer resin+plasticizer) and the variousadditives of the printing pate for forming the step absorbing layers 20are similar to the ones used for the slurry of the green sheet. Except,they are not necessary the same with the ones used for the slurry of thegreen sheet, and can be different. Although the thickness of the stepabsorbing layers 20 is not particularly limited, it is preferably 50 to100% with respect to the thickness of the internal electrode patternlayer 12 a.

Note a prescribed number of the inside green sheets 10 a and theinternal electrode pattern layers 12 a may be alternately laminateddirectly on the outside green sheet 11 a, instead of laminating theinternal laminated body 13 a on the outside green sheet 11 a. Inaddition, a laminated body unit, in which a plurality of the insidegreen sheets 10 a and a plurality of the internal electrode patternlayers 12 a are alternately laminated, may be preliminary manufactured;and a predetermined number of said laminated body units may be laminatedon the outside green sheet 11 a.

As shown in FIGS. 5A and 5B, the obtained green laminated body 4 a iscut to a predetermined size along, e.g. the cut line C, making the greenchips. The plasticizer is removed and the green chips are solidified bydrying and solidification of the green chips. The green chips afterdrying and solidification are put in a barrel container with a media anda polishing solution, and barrel polished by such as a horizontalcentrifugal barrel machine. The green chips after the barrel polish arewashed with water and dried. The capacitor element body 4 shown in FIG.1 can be obtained by carrying out a de-binder process, a firing processand an anneal process when required to the green chips after drying.Note FIGS. 5A and 5B are only the schematic cross-sectional views, andlaminating numbers or the dimensional relations differ from the actual.

An end polishing by such as barrel polish is carried out to the thusobtained sintered body (element body 4), the paste for the terminalelectrode is fired on the sintered body, and the terminal electrodes 6and 8 are obtained. Then, plating or other method is carried out on theterminal electrodes 6 and 8 when required forming the pad layer. Notethe paste for the terminal electrode can be prepared similar to thepaste for internal electrode pattern layer mentioned above.

Thus manufactured multilayer ceramic capacitor 2 is implemented on aprinting substrate and so on by such as soldering, and is used forvarious electronic equipments.

According to the multilayer ceramic capacitor 2 of the presentembodiment, the thickness of the dielectric layer 10 is 0.4 μm or less,the width W0 is 0.59 mm or less, the gap Wgap is 0.010 to 0.025 mm, anda ratio of the gap with respect to the width: Wgap/W0 is 0.025 or more.Thus, even when the thickness of the dielectric layer is made thin,generation of the cracks can be prevented and the decrease of thecapacitance is less.

Note the present invention is not limited to the embodiments describedabove, and can be variously modified within the range of the invention.

For instance, according to the general manufacturing method describedabove, the particle size of the dielectric particles included in thedielectric paste as materials forming each dielectric grainsconstituting the inside dielectric layer 10, the exterior area 11, thelead-out areas 15A and 15B, shown in FIGS. 1 and 2 are approximately thesame. Therefore, in the multilayer ceramic capacitor 2 shown in FIGS. 1and 2 obtained as a result, in case that the thickness of the dielectriclayer 10 sandwiched between the internal electrode layers 12 is 0.4 μmor less, the average grain size of the dielectric grains in thedielectric layer 10 sandwiched between the internal electrode layers 12is relatively larger than the same of the dielectric grains in thearears 11, 15A and 15B, which are not sandwiched between the internalelectrode layers 12. The cause may be considered that a particle growthof dielectric particles in the dielectric layer 10 sandwiched betweenthe internal electrode layers 12 are likely to progress.

Namely, according to the embodiment above, in case that an average grainsize of the first dielectric grains constituting the dielectric layer 10is Di and an average grain size of the second dielectric grains in anexterior area 11 is Dg, Dg/Di<1 is satisfied. Further, according to theembodiment above, in case that an average grain size of the thirddielectric grains constituting the lead-out areas 15A and 15B is Dh,Dh/Di<1 is satisfied. Further, in case that the average grain size ofthe forth dielectric grains constituting the side protection region 16is Dh′, Dh′/Di<1 is satisfied.

Thus, according to the manufacturing method of the other embodiment ofthe invention, the average particle size of the dielectric particles asan dielectric paste material constituting the inside dielectric layer 10shown in FIGS. 1 and 2 is made large, relative to the same of thedielectric particles included in the dielectric paste material formingeach dielectric grain constituting the exterior area 11 and/or thelead-out areas 15 A and 15B. Or otherwise, the average particle size ofthe dielectric particles as an dielectric paste material constitutingthe inside dielectric layer 10 is made small, relative to the same ofthe dielectric particles included in the dielectric paste materialforming each dielectric grains constituting the exterior area 11 and/orthe lead-out areas 15 A and 15B.

As a result, the capacitor element body 4 after firing satisfy therelations of either Dg/Di≧1, Dh/Di≧1 or Dh′/Di≧1, or all of saidrelations can be satisfied. The followings can be considered for thecause. As the particle size of the dielectric particles in thedielectric paste materials is small, said dielectric particles becomethermally active and that the particle growth is easily generated duringfiring. Therefore, by making the average grain size of the dielectricgrains constituting the exterior area 11 and/or the lead-out areas 15 Aand 15B smaller than the same of the dielectric grains constituting theinside dielectric layer 10, which is the capacitance part, thedielectric grains constituting the exterior area 11 and/or the lead-outareas 15 A and 15B are more easy to generate the particle growth thanthe dielectric grains constituting the inside dielectric layer 10, whichis the capacitance part. Then, as a result, the dielectric grains of theexterior area 11 and/or the lead-out areas 15 A and 15B can be madelarger.

With the relations above, the capacitance further improves even when theinside dielectric layer 10 is thinned. It has been reported that thespecific permittivity generally decreases as the inside dielectric layer10 becomes thin. The present inventors, however, have found that thedecrease of the specific permittivity can be suppressed even when theinside dielectric layer 10 is thinned by controlling the grain size ofthe dielectric grains in the specific areas.

Further, in the invention, the relations above may be satisfied in thecapacitor element body 4 after firing by a method other than varying theaverage particle size of the dielectric particles in the dielectricpaste material. For instance, the composition of the dielectricparticles as the dielectric paste material constituting the insidedielectric layer 10 may be different from the composition of thedielectric particles included in the dielectric paste material formingeach dielectric particles constituting the exterior area 11 and/or thelead-out areas 15 A and 15B. For instance, the composition of thedielectric particles included in the dielectric paste material formingeach dielectric particles constituting the exterior area 11 and/or thelead-out areas 15 A and 15B may be made to more easily generate theparticle growth.

The particle size of the dielectric grains after firing can be alsocontrolled by interposing a dummy electrode, not connected to theterminal electrodes 6 and 8, between outside dielectric green sheets 11a at the exterior area 11.

Note the multilayer ceramic electronic device of the invention can beapplied not only to the multilayer ceramic capacitor, but to the othermultilayer type ceramic electronic device. As the other multilayer typeceramic electronic device, all the electronic devices, in which thedielectric layers are laminated via internal electrode can be mentioned;and for instance, band-pass filter, inductor, multilayer three-terminalfilter, piezoelectric element, PTC thermistor, NTC thermistor, varistorand so on can be mentioned.

EXAMPLES

Hereinafter, the present invention will be described based on thefurther details of the examples; however, the invention is not limitedto the examples.

Example 1

Firstly, {(Ba_(1-x-y) Ca_(x) Sr_(y))O}_(u)(Ti_(1-z)Zr_(z))_(v)O₃ powder(x=0.05, y=0, z=0.05 and u/v=1.004) having the average particle size of100 nm as a powdery material of the main material was prepared. Next,MgCO₃, MnCO₃, Y₂O₃, SiO₂ were respectively prepared as subcomponents.Note the subcomponents were preliminary broken down in advance andprocessed to around 40 nm, which is smaller than the particle size ofbarium titanate raw materials.

Next, each powdery material prepared above was weighed by thefollowings. 0.5 moles of MgCO₃ powder, 0.3 moles of MnCO₃ powder, 0.2moles of Y₂O₃ powder, and 2 moles of SiO₂ powder, with respect to 100moles of the main material were weighed. Said each powdery material waswet mixed for 20 hours with ball mill, and dried thereof to obtain adielectric raw material at the capacitance part. The added MgCO₃ andMnCO₃ were included in the dielectric ceramic composition after firingas MgO and MnO, respectively.

Next, 100 parts by weight of the obtained dielectric raw material, 10parts by weight of polyvinyl butyral resin, 5 parts by weight of dioctylphthalate (DOP) as the plasticizer, and 100 parts by weight of analcohol as the solvent were mixed by a ball-mill and were pasted toobtain a dielectric layer paste of the capacitance region 14.

Further, in addition to above, 44.6 parts by weight of Ni particles, 52parts by weight of terpineol, 3 parts by weight of ethyl cellulose and0.4 parts by weight of benzotriazole were kneaded by a triple-roll,pasted thereof to manufacture an internal electrode layer paste.

Further, as the dielectric raw material of the exterior area 11, apowdery main material having the average particle size of 100 nm, whichis the same with that of the dielectric particles in the capacitanceregion 14, was prepared. Said powdery main material was wet-mixed andpasted with the subcomponents, and obtained a dielectric paste for theexterior area.

The dielectric layer paste manufactured above was used to form the greensheet on a PET film. The thickness of the green sheet was adjusted toobtain the thickness td of the dielectric layers after firing asdescribed in Table 1. Next, an electrode layer was printed thereon in apredetermined pattern by using the internal electrode layer paste. Thethickness of the electrode layer in the predetermined pattern wasadjusted to obtain the thickness to of the internal electrode layersafter firing as described in Table 1.

Further, in order to absorb steps, where the electrodes are not printed,the step absorbing layer 20 was formed by carrying out the patternprinting using the same as the dielectric paste in the capacitanceregion 14, and the green sheet 10 a having the internal electrodepattern layers 12 a and the step absorbing layers 20 was manufactured.

Next, the dielectric paste for forming the exterior area 11 was used toform the green sheet on a PET film. The thickness of the green sheet forforming the exterior area 11 was 10 μm. At the time, the green sheet forforming the exterior area 11 was formed by using the green sheet usingthe dielectric raw material of 100 nm.

Plurality of the green sheets for the interior area 13 having theinternal electrode layers and plurality of the green sheets for theexterior area 11 were laminated; and adhered thereof by pressure toobtain a green laminated body. The green laminated body was then cut toa predetermined size to obtain the green chips.

Next, the binder removal process, the firing and the annealing werecarried out to the obtained green chip under the following conditions,and obtained a multilayer ceramic fired body.

The binder removal process was performed under a rate of temperatureincrease of 25° C./hour, a holding temperature of 235° C., a holdingtime of 8 hours, and an atmosphere of air.

Firing conditions were the rate of temperature increase of 600 to 1,000°C./hour, the holding temperature of 1,100 to 1150° C., the holding timeof 1 hour, and a rate of temperature decrease of 200° C./hour, and theatmospheric gas was a humidified N₂+H₂ mixed gas (an oxygen partialpressure of 10⁻¹² MPa).

Annealing conditions were the rate of temperature increase of 200°C./hour, the holding temperature of 1,050° C., the holding time of 3hours, the rate of temperature decrease of 200° C./hour, and theatmospheric gas of a humidified N₂ gas (an oxygen partial pressure: 10⁻⁷MPa).

Note a wetter was used to humidify the atmospheric gas when firing andannealing.

Next, after polishing end faces of the obtained multilayer ceramic firedbody, Cu paste as the external electrode was coated thereon, and thenfiring processing was performed in a reduced atmosphere to obtain samplenumbers 1 to 25 of the multilayer ceramic capacitor samples(hereinafter, sometimes merely referred to as “capacitor sample”) asshown in Table 1.

The lengthwise L0, the width W0 and the width W gap of the obtainedcapacitor sample were varied for each sample, as shown in Table 1.

The capacitance and the crack generation rate of the obtained capacitorsamples were respectively confirmed by the following methods.

(The Capacitance)

Capacitances of the capacitor samples were measured at a referencetemperature of 25° C. by digital LCR meter under the conditions offrequency at 1 kHz and input signal level (measured voltage) at 1.0Vrms. The numerical value of the capacitance shown in Table 1 is shownas a capacitance ratio, by determining the capacitance of thecapacitance element body, showing Wgap of 0.020 with respect to apredetermined L0 and W0, as 1. For instance, the capacitance of samplenumbers 3 to 7 are the ratios referring to the capacitance of samplenumber 5. The capacitances of 0.90 or more were determined good. Resultsare shown in Table 1.

(The Crack Generation Rate)

A measurement method of the crack generation rate is as follows. Saidratio is the cracks detected ratio by visually observing the outwardappearance of the manufactured samples (n=1,000) using such as amicroscope. The crack generation rate of 0 to 1.0 were determined good,and 0 to 0.1 were determined particularly good. Results are shown inTable 1.

TABLE 1 Thickness of Thickness of Crack Wgap dielectric layers internalelectrode generation Capacitance No. L0 [mm] W0 [mm] [mm] Wgap/W0 td[μm] te [μm] rate [%] ratio 1 1.60 0.80 0.025 0.031 0.4 0.4 6.5 0.98 21.60 0.80 0.020 0.025 0.4 0.4 3 1 3 1.02 0.59 0.030 0.051 0.4 0.4 0 0.884 1.02 0.59 0.025 0.042 0.4 0.4 0.6 0.99 5 1.02 0.59 0.020 0.034 0.4 0.40.6 1 6 1.02 0.59 0.015 0.025 0.4 0.4 1 1.01 7 1.02 0.59 0.010 0.017 0.40.4 34 1.04 8 0.620 0.470 0.030 0.064 0.4 0.4 0 0.89 9 0.620 0.470 0.0250.053 0.4 0.4 0 0.96 10 0.620 0.470 0.020 0.043 0.4 0.4 0.2 1 11 0.6200.470 0.015 0.032 0.4 0.4 0.1 1.05 12 0.620 0.470 0.013 0.028 0.4 0.40.8 1.09 13 0.620 0.470 0.010 0.021 0.4 0.4 30 1.12 14 0.620 0.350 0.0300.086 0.4 0.4 0 0.87 15 0.620 0.350 0.025 0.071 0.4 0.4 0 0.94 16 0.6200.350 0.020 0.057 0.4 0.4 0 1 17 0.620 0.350 0.015 0.043 0.4 0.4 0.11.08 18 0.620 0.350 0.010 0.029 0.4 0.4 0.4 1.14 19 0.620 0.350 0.0050.014 0.4 0.4 40 1.15 20 0.380 0.185 0.030 0.162 0.4 0.4 0 0.79 21 0.3800.185 0.025 0.135 0.4 0.4 0 0.9 22 0.380 0.185 0.020 0.108 0.4 0.4 0 123 0.380 0.185 0.015 0.081 0.4 0.4 0 1.05 24 0.380 0.185 0.010 0.054 0.40.4 0.5 1.19 25 0.380 0.185 0.005 0.027 0.4 0.4 19 1.27

Example 2

As shown in Table 2, samples of the multilayer ceramic capacitors weremanufactured similarly with Example 1, except the thickness td of thedielectric layer 10 after firing and the thickness to of the internalelectrode layers 12 after firing were 0.3 μm. The capacitance and thecrack generation rate thereof were respectively measured similarly withExample 1. Results are shown in Table 2.

TABLE 2 Crack Thickness of Thickness of generation Wgap dielectriclayers internal electrode rate Capacitance No. L0 [mm] W0 [mm] [mm]Wgap/W0 td [μm] te [μm] [%] ratio 26 1.02 0.59 0.025 0.042 0.3 0.3 0.60.96 27 1.02 0.59 0.020 0.034 0.3 0.3 0.7 1 28 1.02 0.59 0.015 0.025 0.30.3 0.9 1.01 29 1.02 0.59 0.010 0.017 0.3 0.3 28 1.08 30 0.620 0.4700.025 0.053 0.3 0.3 0.2 0.97 31 0.620 0.470 0.020 0.043 0.3 0.3 0.2 1 320.620 0.470 0.015 0.032 0.3 0.3 0.3 1.06 33 0.620 0.470 0.013 0.028 0.30.3 0.9 1.07 34 0.620 0.470 0.010 0.021 0.3 0.3 40 1.11 35 0.620 0.3500.030 0.100 0.3 0.3 0 0.87 36 0.620 0.350 0.025 0.071 0.3 0.3 0.1 0.9537 0.620 0.350 0.020 0.057 0.3 0.3 0 1 38 0.620 0.350 0.015 0.043 0.30.3 0.3 1.05 39 0.620 0.350 0.010 0.029 0.3 0.3 1 1.07 40 0.620 0.3500.005 0.014 0.3 0.3 46 1.19 41 0.380 0.185 0.030 0.162 0.3 0.3 0 0.82 420.380 0.185 0.025 0.135 0.3 0.3 0 0.95 43 0.380 0.185 0.020 0.108 0.30.3 0.3 1 44 0.380 0.185 0.015 0.081 0.3 0.3 0 1.12 45 0.380 0.185 0.0100.054 0.3 0.3 0.8 1.17 46 0.380 0.185 0.005 0.027 0.3 0.3 13 1.34

Evaluation 1

From the results shown in Tables 1 and 2, it was confirmed that themultilayer ceramic capacitor with low crack generation rate and lessdecrease in the capacitance can be obtained, when the thickness td ofthe dielectric layers is 0.4 μm or less, the width W0 is 0.59 mm orless, the gap Wgap is 0.010 to 0.025 mm, and the ratio (Wgap/W0) is0.025 or more.

Example 3

Samples of the multilayer ceramic capacitors were manufactured similarlywith Example 1, except the thickness to of the internal electrode layers12 after firing were varied. The capacitance and the crack generationrate thereof were respectively measured similarly with Example 1.Results are shown in Table 3.

TABLE 3 Crack Thickness of Thickness of generation Wgap dielectriclayers internal electrode rate Capacitance No. L0 [mm] W0 [mm] [mm]Wgap/W0 td [μm] te [μm] te/td [%] ratio  4a 1.02 0.59 0.025 0.042 0.40.38 0.95 0.5 0.94  4b 1.02 0.59 0.025 0.042 0.4 0.42 1.05 0.8 1  4c1.02 0.59 0.025 0.042 0.4 0.5 1.25 5 1.03 15a 0.620 0.350 0.025 0.0710.4 0.38 0.95 0 0.91 15b 0.620 0.350 0.025 0.071 0.4 0.42 1.05 0.5 0.9415c 0.620 0.350 0.025 0.071 0.4 0.5 1.25 10 0.96 17a 0.620 0.350 0.0150.043 0.4 0.38 0.95 0.1 1.08 17b 0.620 0.350 0.015 0.043 0.4 0.42 1.050.3 1.1 17c 0.620 0.350 0.015 0.043 0.4 0.5 1.25 22 1.16 23a 0.380 0.1850.015 0.081 0.4 0.38 0.95 0 0.95 23b 0.380 0.185 0.015 0.081 0.4 0.421.05 0 1.04 23c 0.380 0.185 0.015 0.081 0.4 0.5 1.25 11 1.14 24a 0.3800.185 0.010 0.054 0.4 0.38 0.95 0.4 0.98 24b 0.380 0.185 0.010 0.054 0.40.42 1.05 0.7 1.01 24c 0.380 0.185 0.010 0.054 0.4 0.5 1.25 17 1.04

Evaluation 2

From the results shown in Table 3, it was confirmed that the multilayerceramic capacitor with low crack generation rate and less decrease inthe capacitance can be obtained, when te/td is less than 1.25 andparticularly preferably te/td is 0.95 to 1.05.

Example 4

As shown in Table 4, samples (sample numbers 16a and 16b) of themultilayer ceramic capacitors were manufactured similarly with sample 16of Example 1, except the average grain size Dg of the dielectric grainsin the exterior area 11 was varied relative to the average grain size Diof the dielectric grains in the capacitance region 14. The capacitanceand the crack generation rate thereof were respectively measuredsimilarly with sample 16 of Example 1. Results are shown in Table 4. Inorder to obtain the relation: Dg/Di is 1 or more, the average particlesize of the dielectric particles in the raw material included in thedielectric paste forming the exterior area 11 was determined 60 nm.

Example 5

As shown in Table 5, samples (sample numbers 16c and 16d) of themultilayer ceramic capacitors were manufactured similarly with sample 16of Example 1, except the average grain size Dh of the dielectric grainsin the lead-out areas 15A and 15B was varied relative to the averagegrain size Di of the dielectric grains in the capacitance region 14. Thecapacitance and the crack generation rate thereof were respectivelymeasured similarly with sample 16 of Example 1. Results are shown inTable 5. In order to obtain the relation: Dh/Di is 1 or more, theaverage particle size of the dielectric particles in the raw materialincluded in the step absorbing dielectric paste forming the lead-outareas 12A and 12B and the side protection region 16 was determined 60nm.

Note the average grain size of the dielectric grains after firing wereconfirmed by the following method.

(The Average Grain Size of the Dielectric)

The capacitor samples were made to stand vertically making thelamination direction upside, and periphery of the samples were embeddedwith a curable resin by using a Tefron (a registered trademark) madevessel of 25 mm size and 20 mm long. Then, samples were grinded to showthe cross-section along the longitudinal direction using the sandpaperand a fine processing grinder; and milling using argon ion was carriedout to remove the damage of the surface.

The dielectric grains in the capacitance region 14, the exterior area 11and the lead-out areas 15A and 15B were observed by magnifying theprocessed samples twenty thousand times using an electron microscope.And using the image analysis system, an equivalent circle size wascalculated from the cross-section areas of 500 grains.

TABLE 4 Thickness of internal Crack Thickness of electrode generationAverage grain size Average grain size L0 Wgap Wgap/ dielectric layers terate Capacitance in capacitance in exterior area Dg No. [mm] W0 [mm][mm] W0 td [μm] [μm] [%] ratio Dg/Di region Di [μm] [μm] 16 0.620 0.3500.020 0.057 0.4 0.4 0 1 0.81 0.33 0.27 16a 0.620 0.350 0.020 0.057 0.40.4 0 1.12 1 0.33 0.33 16b 0.620 0.350 0.020 0.057 0.4 0.4 0 1.22 1.150.33 0.38

TABLE 5 Average Thickness of Crack grain size dielectric Thickness ofgeneration Average grain size in lead-out L0 Wgap layers td internalelectrode rate Capacitance in capacitance areas Dh No. [mm] W0 [mm] [mm]Wgap/W0 [μm] te [μm] [%] ratio Dh/Di region Di [μm] [μm] 16 0.620 0.3500.020 0.057 0.4 0.4 0 1 0.88 0.33 0.29 16c 0.620 0.350 0.020 0.057 0.40.4 0 1.11 1 0.33 0.33 16d 0.620 0.350 0.020 0.057 0.4 0.4 0 1.23 1.230.33 0.41

Evaluation 3

From the results shown in Table 4, it was confirmed that the capacitancefurther improves and the crack generation rate is low, when the relationis preferably Dg/Di≧1, more preferably Dg/Di≧1.05, and the mostpreferably Dg/Di≧1.15.

From the results shown in Table 5, it was confirmed that the capacitancefurther improves and the crack generation rate is low, when the relationis preferably Dh/Di≧1, more preferably Dh/Di≧1.1, and the mostpreferably Dh/Di≧1.2.

Note in Example 5, the average particle size of the dielectric particlesin raw materials included in the step absorbing dielectric paste wasdetermined 60 nm; thus, it was confirmed that it is larger than theaverage grain size Dh′ of the dielectric grains after firing included inthe side protection region 16 shown in FIG. 2 and the average grain sizeDi of the dielectric grains after firing in the capacitance region 14.It is also confirmed that Dh′/Di is almost the same with Dh/Di.

DESCRIPTIONS OF THE NUMERALS

-   2: Multilayer ceramic capacitor-   4: Capacitor element body-   6: The first terminal electrode-   8: The second terminal electrode-   10: Inside dielectric layers-   10 a: Inside green sheet-   11: Exterior area-   11 a: Outside green sheet-   12: Internal electrode layers-   12A, 12B: Lead-out part-   12 a: Internal electrode pattern layer-   13: Interior area-   13 a: Internal laminated body-   14: Capacitance region-   15A, 15B: Lead-out areas-   16: Side protection region-   20: Step absorbing layers

What is claimed is:
 1. A multilayer ceramic electronic devicecomprising: a ceramic element body, in which a plurality of dielectriclayers and a plurality of internal electrode layers are alternatelystacked, and at least a pair of external electrodes which are connectedto the internal electrode layers on surfaces of the ceramic elementbody, wherein a thickness of the dielectric layers is 0.4 μm or less, awidth (W0) of the ceramic element body along a width-direction is 0.59mm or less, a gap (Wgap) between an outer face of the ceramic elementbody and an end of the internal electrode layers along width-directionof the ceramic element body is 0.010 to 0.025 mm, and a ratio (Wgap/W0)of the gap with respect to the width is 0.025 or more.
 2. The multilayerceramic electronic device as set forth in claim 1, wherein a ratio(te/td) of a thickness (td) of the internal electrode layers withrespect to a thickness (te) of the dielectric layers is preferably 1.05or less.
 3. The multilayer ceramic electronic device as set forth inclaim 1, wherein Dg/Di≧1 is satisfied, in case that an average grainsize of the first dielectric grains constituting the dielectric layerplaced between the internal electrode layers along the laminatingdirection is Di and an average grain size of the second dielectricgrains in an exterior area placed outside of the laminating direction ofan interior area, in which the internal electrode layers are laminatedinterposing the dielectric layers along the laminating direction, is Dg.4. The multilayer ceramic electronic device as set forth in claim 2,wherein Dg/Di≧1 is satisfied, in case that an average grain size of thefirst dielectric grains constituting the dielectric layer placed betweenthe internal electrode layers along the laminating direction is Di andan average grain size of the second dielectric grains in an exteriorarea placed outside of the laminating direction of an interior area, inwhich the internal electrode layers are laminated interposing thedielectric layers along the laminating direction, is Dg.
 5. Themultilayer ceramic electronic device as set forth in claim 1, whereinDh/Di≧1 is satisfied, in case that the average grain size of the firstdielectric grains constituting the dielectric layers placed between theinternal electrode layers along the laminating direction is Di, and anaverage grain size of the third dielectric grains constituting alead-out area placed between the lead-out parts of the internalelectrode layers connected to either one of the external electrodes isDh.
 6. The multilayer ceramic electronic device as set forth in claim 2,wherein Dh/Di≧1 is satisfied, in case that the average grain size of thefirst dielectric grains constituting the dielectric layers placedbetween the internal electrode layers along the laminating direction isDi, and an average grain size of the third dielectric grainsconstituting a lead-out area placed between the lead-out parts of theinternal electrode layers connected to either one of the externalelectrodes is Dh.
 7. The multilayer ceramic electronic device as setforth in claim 3, wherein Dh/Di≧1 is satisfied, in case that the averagegrain size of the first dielectric grains constituting the dielectriclayers placed between the internal electrode layers along the laminatingdirection is Di, and an average grain size of the third dielectricgrains constituting a lead-out area placed between the lead-out parts ofthe internal electrode layers connected to either one of the externalelectrodes is Dh.
 8. The multilayer ceramic electronic device as setforth in claim 4, wherein Dh/Di≧1 is satisfied, in case that the averagegrain size of the first dielectric grains constituting the dielectriclayers placed between the internal electrode layers along the laminatingdirection is Di, and an average grain size of the third dielectricgrains constituting a lead-out area placed between the lead-out parts ofthe internal electrode layers connected to either one of the externalelectrodes is Dh.